Structural Fire Suit Layers Explained

A structural firefighting suit typically consists of three key layers to provide protection against heat, flames, and other hazards encountered during firefighting operations.

Outer Shell

This is the outermost layer of the suit and is made of a fire-resistant material. It provides protection against direct flame exposure, radiant heat, and abrasions. Firefighting suits are constructed using various fire-resistant fibres, such as PBI, PBO, Nomex, Kermel, Conex, Twaron, Kevlar, or other unbranded materials. Each fibre has unique properties that contribute to the performance of the suit. However, no single fibre is perfect for every aspect of the suit’s design.

Therefore, manufacturers create composites using different fibres to take advantage of their strengths and mitigate their weaknesses. If a suit were constructed using only one type of fibre, it would not be suitable for firefighting operations due to its limitations. By combining different fibres, the suit can provide optimal protection against the hazards of a fire.

Moisture Barrier

The moisture barrier is a layer that keeps moisture and liquids from penetrating the suit. It is typically made of a breathable material such as Gore-Tex or PTFE and is essential for maintaining the comfort of the firefighter. The moisture barrier plays a vital role in a firefighting suit, as it prevents water from penetrating the suit while allowing moisture to escape to keep the firefighter comfortable.

All seams on the moisture barrier are taped for added protection. Additionally, the moisture barrier layer provides thermal protection as it typically includes a non-woven aramid laminated to one side. It is important to regularly check the moisture barrier for damage, as any breach in the barrier can lead to serious injuries from steam burns. It is critical to ensure its durability, breathability, and waterproof capabilities.

Thermal Barrier

This layer provides insulation against heat and flames and is typically made of a material such as aramid or carbon. It is designed to prevent the transfer of heat from the outer layer to the inner layers of the suit. The thermal liner we use is our suits is the Twin Spacer.

It’s also worth noting that the Thermal liner of a suit is a critical component in its overall thermal performance. Without an effective liner, even the best outer shell would not provide adequate protection against heat and flames. Therefore, the Twin Spacer’s exceptional thermal performance, combined with its lightweight design and air gap construction, make it an ideal choice for a wide range of applications where reliable thermal protection is essential.

What Is An Arc Flash?

An arc flash is a sudden release of electrical energy that occurs when current jumps across a gap between two conductors or from a conductor to a ground. The arc flash generates an intense burst of heat and light that can cause serious injuries, damage to equipment, and fires.

Arc flashes can occur in a wide range of electrical systems and equipment, including switchgear, transformers, motors, and other high-voltage components. They can be caused by a variety of factors, including equipment failure, human error, or a short circuit.

The intense heat generated by an arc flash can cause severe burns, as well as ignite clothing and other materials in the surrounding area, leading to secondary fires. The bright light from the arc flash can also cause temporary or permanent vision damage.

To prevent arc flash incidents, it’s important to follow proper electrical safety procedures, including wearing appropriate personal protective equipment (PPE), de-energizing equipment before working on it, and maintaining a safe distance from energized equipment.

Understanding Arc Ratings and Calories

Now that you understand FR clothing is tested and given an arc rating, you know that the arc rating measures the amount of heat the flame resistant fabric blocks when exposed to electric arc. The arc rating is the number of calories that the garment is expected to “absorb” if exposed to an electric arc. Arc rating is, in essence, the level of protection provided to you, the wearer.

Calorie is the unit of measure of the heat energy of an arc flash and the protective level of FR clothing. The bigger the calorie number, the greater the heat energy level of arc flash and the greater the protective level of the clothing. You will be protected from an electric arc if your clothing has a higher calorie arc rating than the calories of heat generated by the arc.

While it does not matter if the fabric has an Ebt,  ATPV and or ELIM value, it is important to pay attention to the calorie level the fabric can support* (as expressed in cal/cm2)